1. Field of the Invention
This invention relates generally to determining the level of fluid in a container. More particularly the invention pertains to sensing the temperature of the fluid.
2. Description of the Prior Art
Accurately measuring transmission oil or engine crankcase oil level in a repeatable manner has been challenging because, when the dipstick is pulled out of a fill tube, the oil level is not clearly indicated. An oil film left on the dipstick does not provide a clearly visible demarcation. In addition, the dipstick can contact the side of the fill tube causing oil film to be formed in areas above where the actual oil level is located. This results in a measurement system that does not provide a repeatable, reliable indication of the oil level in the vehicle.
Additionally, transmission oil should be warmed to be about 150° F. before reading the oil level. Often the vehicle operator or service technician has no easy technique way to determine transmission oil temperature without the use of a diagnostic tool. Transmission oil level is very important in automatic transmission function since too much oil may reduce fuel economy and can result in venting fluid. Too little oil degrades function under cold conditions. These constraints often lead to a very tight oil level tolerance (about 0.5 liters), which may be difficult to verify using conventional dipsticks.
There is a need in the industry for a fluid level indicator that responds to fluid temperature and provides clear, reliable, visible indication of fluid level in a confined space, such as a transmission oil sump or an engine crankcase.